The use of cytotoxic agents in, for example, chemotherapy of cancer patients almost inevitably causes hair loss known as alopecia. Alopecia can be prevented by cooling the scalp because drug uptake by hair follicles is reduced as a consequence of cutaneous vasoconstriction and the inhibition of cellular metabolic pathways. Cooling can be achieved in a number of ways: by circulating chilled liquid in close thermal contact with the scalp; by the application of crushed ice packs or shaped cryogel packs; by the activation of endothermic chemical reactions, and by the circulation of cold air over the scalp.
Cold air scalp cooling has several advantages over the other cooling methods. Firstly it requires no additional thermal contact medium thus, unlike all the other methods, hair wetting is not required. The technique can be applied with very little weight being imposed on the patients head and is therefore much less tiring and uncomfortable, and thermal transfer can be optimised over the entire scalp by design of the applicator helmet.
Clinical trials have been performed using a vortex tube air refrigerator as described in the paper entitled "Adriamycin Alopecia Prevented by Cold Air Scalp Cooling" published in American Journal of Clinical Oncology (CCT) 9(5):454-457, 1986 by Symonds McCormick and Maxted. This disclosure established the requirements for temperature and air flow and demonstrated that clinical results, equalling or exceeding any previously published, could be achieved without skill of application or degree of preparation required for any of the other methods.
However the use of standard refrigeration components to provide a source of cold air has a number of problems. Namely freezing of entrained moisture on the evaporator causes low efficiency due to latent heat loses and airflow obstruction and the circulating fan causes significant heat gain. The helmet and tubing design described in the above paper did not permit sufficient free flow of air to avoid significant pressure drops.